PVC materials that can be used to produce seals that expand in fire conditions to prevent the passage of toxic fumes and smoke have been launched by Dugdale plc, manufacturer of PVC compounds and dry blends.

The PVC compounds incorporate specially treated graphite flakes that add intumescent properties. At a temperature of around 250°C the layers in each graphite flake separate and this increases the volume of the PVC material by approximately 300 percent. In a fire situation, this reaction would typically be triggered by hot smoke.

Foam and solid grades are offered. The foam type is designed to produce seals for panels and partitions in offices and buildings. Its foam properties allow it sufficient recovery to act as a barrier to noise, dust and draughts while accommodating some movement in the building structure. What makes it quite unlike other foam seals that melt and leave gaps through which toxic gases and smoke can pass, is its capacity to expand to fill gaps and the PVC char that remains retains sufficient strength to resist penetrationThe solid material has been developed especially for door edge seals and for wrapping pipes and cables where they pass through walls and under floors.

Both compounds are available in extrusion and injection moulding grades. Applications are expected in sound and insulation panels, bulkheads and partitions across many industries; for example, office furniture, building and transport, where the spread of toxic fumes and smoke is considered to be hazardous to health.

Fire door strip can expand substantially in volume to form a dense char to prevent the penetration of gas, smoke and flames in the event of a fire. It is developed mainly with expandable graphite, which has abundant sources in China.